* calendar/todos.el: Extend and improve handling of item editing,

especially of date/time header.
(todos-month-name-array, todos-month-abbrev-array): New defconsts.
(todos-date-pattern): Use explicitly numbered groups.
(todos-read-date): Optionally read and return just one of the date
string components year, month or monthname, day.
(todos-key-bindings): Add bindings for new item header editing
commands.
(todos-edit-item): Exclude date/time header from minibuffer by
default; include it by passing a prefix argument.
(todos-edit-item-header-1): New function containing the guts of
the commands for editing item date/time headers.
(todos-edit-item-header): Use it.  Condition editing of time
string on value of `todos-always-add-time-string'.
(todos-edit-item-date-from-calendar): Use todos-edit-item-header-1.
(todos-edit-item-date-to-today): Rename from
todos-edit-item-date-is-today and use todos-edit-item-header-1.
(todos-edit-item-date): Remove.
(todos-edit-item-date-day-name, todos-edit-item-date-year)
(todos-edit-item-date-month, todos-edit-item-date-day): New commands.

2 files changed, 374 insertions, 133 deletions

diff --git a/lisp/ChangeLog b/lisp/ChangeLog
index 98df5d3fe92..bde403fe0d5 100644
--- a/lisp/ChangeLog
+++ b/lisp/ChangeLog
@@ -1,3 +1,26 @@
+2012-12-12  Stephen Berman  <stephen.berman@gmx.net>
+
+        * calendar/todos.el: Extend and improve handling of item editing,
+        especially of date/time header.
+        (todos-month-name-array, todos-month-abbrev-array): New defconsts.
+        (todos-date-pattern): Use explicitly numbered groups.
+        (todos-read-date): Optionally read and return just one of the date
+        string components year, month or monthname, day.
+        (todos-key-bindings): Add bindings for new item header editing
+        commands.
+        (todos-edit-item): Exclude date/time header from minibuffer by
+        default; include it by passing a prefix argument.
+        (todos-edit-item-header-1): New function containing the guts of
+        the commands for editing item date/time headers.
+        (todos-edit-item-header): Use it.  Condition editing of time
+        string on value of `todos-always-add-time-string'.
+        (todos-edit-item-date-from-calendar): Use todos-edit-item-header-1.
+        (todos-edit-item-date-to-today): Rename from
+        todos-edit-item-date-is-today and use todos-edit-item-header-1.
+        (todos-edit-item-date): Remove.
+        (todos-edit-item-date-day-name, todos-edit-item-date-year)
+        (todos-edit-item-date-month, todos-edit-item-date-day): New commands.
+
 2012-12-02  Stephen Berman  <stephen.berman@gmx.net>
 
         * calendar/todos.el (todos-show): Fix a comment.
diff --git a/lisp/calendar/todos.el b/lisp/calendar/todos.el
index 70f144d8004..c7f2d5b8dee 100644
--- a/lisp/calendar/todos.el
+++ b/lisp/calendar/todos.el
@@ -1336,19 +1336,32 @@ it.")
 
 ;;; Global variables and helper functions for items
 
+(defconst todos-month-name-array
+  (vconcat calendar-month-name-array (vector "*"))
+  "Array of month names, in order.
+The final element is \"*\", indicating an unspecified month.")
+
+(defconst todos-month-abbrev-array
+  (vconcat calendar-month-abbrev-array (vector "*"))
+  "Array of abbreviated month names, in order.
+The final element is \"*\", indicating an unspecified month.")
+
 (defconst todos-date-pattern
   (let ((dayname (diary-name-pattern calendar-day-name-array nil t)))
-    (concat "\\(?:" dayname "\\|"
+    (concat "\\(?5:" dayname "\\|"
             (let ((dayname)
                   ;; FIXME: how to choose between abbreviated and unabbreviated
                   ;; month name?
-                  (monthname (format "\\(?:%s\\|\\*\\)"
-                                     (diary-name-pattern
-                                      calendar-month-name-array
-                                      calendar-month-abbrev-array t)))
-                  (month "\\(?:[0-9]+\\|\\*\\)")
-                  (day "\\(?:[0-9]+\\|\\*\\)")
-                  (year "-?\\(?:[0-9]+\\|\\*\\)"))
+                  ;; (monthname (format "\\(?6:%s\\|\\*\\)"
+                  ;;                 (diary-name-pattern
+                  ;;                  calendar-month-name-array
+                  ;;                  calendar-month-abbrev-array)))
+                  (monthname (format "\\(?6:%s\\)" (diary-name-pattern
+                                                    todos-month-name-array
+                                                    todos-month-abbrev-array)))
+                  (month "\\(?7:[0-9]+\\|\\*\\)")
+                  (day "\\(?8:[0-9]+\\|\\*\\)")
+                  (year "-?\\(?9:[0-9]+\\|\\*\\)"))
               (mapconcat 'eval calendar-date-display-form ""))
             "\\)"))
   "Regular expression matching a Todos date header.")
@@ -1637,57 +1650,87 @@ TYPE can be either a file or a category"
     name))
 
 ;; Adapted from calendar-read-date and calendar-date-string.
-(defun todos-read-date ()
+(defun todos-read-date (&optional arg mo yr)
   "Prompt for Gregorian date and return it in the current format.
-Also accepts `*' as an unspecified month, day, or year."
-  (let* ((year (let (x)
-                 (while (if (numberp x) (< x 0) (not (eq x '*)))
-                   (setq x (read-from-minibuffer
-                            "Year (>0 or RET for this year or * for any year): "
-                            nil nil t nil (number-to-string
-                                           (calendar-extract-year
-                                            (calendar-current-date))))))
-                 x))
-         (month-array (vconcat calendar-month-name-array (vector "*")))
-         (abbrevs (vconcat calendar-month-abbrev-array (vector "*")))
-         (completion-ignore-case todos-completion-ignore-case)
-         (monthname (completing-read
-                     "Month name (RET for current month, * for any month): "
-                     (mapcar 'list (append month-array nil))
-                     nil t nil nil
-                     (calendar-month-name (calendar-extract-month
-                                           (calendar-current-date)) t)))
-         (month (cdr (assoc-string
-                      monthname (calendar-make-alist month-array nil nil
-                                                     abbrevs))))
-         (last (if (= month 13)
-                   ;; Use longest possible month for checking day number
-                   ;; input.  Does Calendar do anything special when * is
-                   ;; currently a shorter month?
-                   31
-                 (let ((yr (if (eq year '*)
-                               ;; Use a leap year to allow Feb. 29.
-                               2012
-                             year)))
-                   (calendar-last-day-of-month month yr))))
-         (day (let (x)
-                (while (if (numberp x) (or (< x 0) (< last x)) (not (eq x '*)))
-                  (setq x (read-from-minibuffer
-                           (format
-                            "Day (1-%d or RET for today or * for any day): "
-                            last) nil nil t nil (number-to-string
-                                                 (calendar-extract-day
-                                                  (calendar-current-date))))))
-                 x))
-         dayname)                       ; Needed by calendar-date-display-form.
-    (setq year (if (eq year '*) (symbol-name '*) (number-to-string year)))
-    (setq day (if (eq day '*) (symbol-name '*) (number-to-string day)))
-    ;; FIXME: make abbreviation customizable
-    (setq monthname
-          (or (and (= month 13) "*")
-              (calendar-month-name (calendar-extract-month (list month day year))
-                                   t)))
-    (mapconcat 'eval calendar-date-display-form "")))
+
+With non-nil ARG, prompt for and return only the date component
+specified by ARG, which can be one of these symbols:
+`month' (prompt for name, return name or number according to
+value of `calendar-date-display-form'), `day' of month, or
+`year'.  The value of each of these components can be `*',
+indicating an unspecified month, day, or year.
+
+When ARG is `day', non-nil arguments MO and YR determine the
+number of the last the day of the month."
+  (let (year monthname month day
+             dayname)                   ; Needed by calendar-date-display-form.
+    ;; FIXME: year can be omitted from Diary
+    (when (or (not arg) (eq arg 'year))
+      (while (if (natnump year) (< year 1) (not (eq year '*)))
+        (setq year (read-from-minibuffer
+                    "Year (>0 or RET for this year or * for any year): "
+                    nil nil t nil (number-to-string
+                                   (calendar-extract-year
+                                    (calendar-current-date)))))))
+    (when (or (not arg) (eq arg 'month))
+      (let* ((marray todos-month-name-array)
+             (mlist (append marray nil))
+             (mabarray todos-month-abbrev-array)
+             (mablist (append mabarray nil))
+             (completion-ignore-case todos-completion-ignore-case))
+        (setq monthname (completing-read
+                         "Month name (RET for current month, * for any month): "
+                         ;; (mapcar 'list (append marray nil))
+                         mlist nil t nil nil
+                         (calendar-month-name (calendar-extract-month
+                                               (calendar-current-date)) t))
+              ;; month (cdr (assoc-string
+              ;;                  monthname (calendar-make-alist marray nil nil
+              ;;                                                 abbrevs))))))
+              month (1+ (- (length mlist)
+                           (length (or (member monthname mlist)
+                                       (member monthname mablist))))))
+        ;; FIXME: We follow diary-insert-entry in using abbreviated
+        ;; month name (and no day name) in date string.  Should this
+        ;; be customizable?
+        (setq monthname (aref mabarray (1- month)))))
+    (when (or (not arg) (eq arg 'day))
+      (let ((last (let ((mm (or month mo))
+                        (yy (or year yr)))
+                    ;; If month is unspecified, use a month with 31
+                    ;; days for checking day of month input.  Does
+                    ;; Calendar do anything special when * is
+                    ;; currently a shorter month?
+                    (if (= mm 13) (setq mm 1))
+                    ;; If year is unspecified, use a leap year to
+                    ;; allow Feb. 29.
+                    (if (eq year '*) (setq yy 2012))
+                    (calendar-last-day-of-month mm yy))))
+        (while (if (natnump day) (or (< day 1) (> day last)) (not (eq day '*)))
+          (setq day (read-from-minibuffer
+                     (format "Day (1-%d or RET for today or * for any day): "
+                             last)
+                     nil nil t nil (number-to-string
+                                    (calendar-extract-day
+                                     (calendar-current-date))))))))
+    ;; Stringify read values (monthname is already a string).
+    (and year (setq year (if (eq year '*)
+                             (symbol-name '*)
+                           (number-to-string year))))
+    (and day (setq day (if (eq day '*)
+                           (symbol-name '*)
+                         (number-to-string day))))
+    (and month (setq month (if (eq month '*)
+                               (symbol-name '*)
+                             (number-to-string month))))
+    (if arg
+        (cond ((eq arg 'year) year)
+              ((eq arg 'day) day)
+              ((eq arg 'month)
+               (if (memq 'month calendar-date-display-form)
+                   month
+                 monthname)))
+      (mapconcat 'eval calendar-date-display-form ""))))
 
 (defun todos-read-dayname ()
   "Choose name of a day of the week with completion and return it."
@@ -1742,6 +1785,7 @@ the empty string (i.e., no time string)."
                    :notify (lambda (widget &rest ignore)
                              (setq todos-multiple-filter-files 'quit)
                              (quit-window t)
+                             ;; FIXME: use (throw 'exit nil) ?
                              (exit-recursive-edit))
                    "Cancel")
     (widget-insert "   ")
@@ -1754,6 +1798,7 @@ the empty string (i.e., no time string)."
                                            (widget-value
                                             todos-multiple-filter-files-widget)))
                              (quit-window t)
+                             ;; FIXME: use (throw 'exit nil) ?
                              (exit-recursive-edit))
                    "Apply")
     (use-local-map widget-keymap)
@@ -2407,7 +2452,7 @@ which is the value of the user option
 (defvar todos-key-bindings
   `(
     ;;               display
-    ("Cd"            . todos-display-categories) ;FIXME: Cs todos-show-categories?
+    ("Cd"            . todos-display-categories) ;FIXME: Fc todos-file-categories?
     ("H"             . todos-highlight-item)
     ("N"             . todos-hide-show-item-numbering)
     ("D"             . todos-hide-show-date-time)
@@ -2420,7 +2465,7 @@ which is the value of the user option
     ("V"             . todos-show-done-only)
     ("As"            . todos-show-archive)
     ("Ac"            . todos-choose-archive)
-    ("Y"             . todos-diary-items)
+    ;; ("Y"          . todos-diary-items)
     ("Fe"            . todos-edit-multiline)
     ("Fh"            . todos-highlight-item)
     ("Fn"            . todos-hide-show-item-numbering)
@@ -2453,9 +2498,12 @@ which is the value of the user option
     ("ee"            . todos-edit-item)
     ("em"            . todos-edit-multiline-item)
     ("eh"            . todos-edit-item-header)
-    ("edd"           . todos-edit-item-date)
     ("edc"           . todos-edit-item-date-from-calendar)
-    ("edt"           . todos-edit-item-date-is-today)
+    ("edt"           . todos-edit-item-date-to-today)
+    ("edn"           . todos-edit-item-date-day-name)
+    ("edy"           . todos-edit-item-date-year)
+    ("edm"           . todos-edit-item-date-month)
+    ("edd"           . todos-edit-item-date-day)
     ("et"            . todos-edit-item-time)
     ("eyy"           . todos-edit-item-diary-inclusion)
     ;; (""           . todos-edit-category-diary-inclusion)
@@ -4209,7 +4257,12 @@ the priority is not given by HERE but by prompting."
                                (string-match todos-date-pattern date-type))
                           (setq todos-date-from-calendar date-type)
                           (todos-set-date-from-calendar))
-                         (t (calendar-date-string (calendar-current-date) t t))))
+                         (t
+                          ;; FIXME: We follow diary-insert-entry in
+                          ;; hardcoding abbreviated month name and no
+                          ;; day name in date string.  Should this be
+                          ;; customizable?
+                          (calendar-date-string (calendar-current-date) t t))))
            (time-string (or (and time (todos-read-time))
                             (and todos-always-add-time-string
                                  (substring (current-time-string) 11 16)))))
@@ -4285,7 +4338,7 @@ the priority is not given by HERE but by prompting."
          (let (calendar-view-diary-initially-flag)
            (calendar))
          ;; *Calendar* is now current buffer.
-         (local-set-key (kbd "RET") 'exit-recursive-edit)
+         (local-set-key (kbd "RET") 'exit-recursive-edit) ; FIXME: (throw 'exit nil)?
          (message "Put cursor on a date and type <return> to set it.")
          ;; FIXME: is there a better way than recursive-edit?
          (recursive-edit)
@@ -4344,13 +4397,18 @@ the item at point."
             (todos-prefix-overlays)))
       (if ov (delete-overlay ov)))))
 
-(defun todos-edit-item ()
+(defun todos-edit-item (&optional arg)
   "Edit the Todo item at point.
+
+With non-nil prefix argument ARG, include the item's date/time
+header, making it also editable; otherwise, include only the item
+content.
+
 If the item consists of only one logical line, edit it in the
 minibuffer; otherwise, edit it in Todos Edit mode."
-  (interactive)
+  (interactive "P")
   (when (todos-item-string)
-    (let* ((buffer-read-only)
+    (let* ((opoint (point))
            (start (todos-item-start))
            (item-beg (progn
                        (re-search-forward
@@ -4359,16 +4417,22 @@ minibuffer; otherwise, edit it in Todos Edit mode."
                                 (regexp-quote todos-nondiary-end) "?")
                         (line-end-position) t)
                        (1+ (- (point) start))))
-           (item (todos-item-string))
+           (header (substring (todos-item-string) 0 item-beg))
+           (item (if arg (todos-item-string)
+                   (substring (todos-item-string) item-beg)))
            (multiline (> (length (split-string item "\n")) 1))
-           (opoint (point)))
+           (buffer-read-only nil))
       (if multiline
-          (todos-edit-multiline t)
-        (let ((new (read-string "Edit: " (cons item item-beg))))
-          (while (not (string-match
-                       (concat todos-date-string-start todos-date-pattern) new))
-            (setq new (read-from-minibuffer
-                       "Item must start with a date: " new)))
+          (todos-edit-multiline-item)
+        (let ((new (concat (if arg "" header)
+                           (read-string "Edit: " (if arg
+                                                     (cons item item-beg)
+                                                   (cons item 0))))))
+          (when arg
+            (while (not (string-match (concat todos-date-string-start
+                                              todos-date-pattern) new))
+              (setq new (read-from-minibuffer
+                         "Item must start with a date: " new))))
           ;; Indent newlines inserted by C-q C-j if nonspace char follows.
           (setq new (replace-regexp-in-string
                      "\\(\n\\)[^[:blank:]]"
@@ -4422,91 +4486,245 @@ in the number or names of categories."
   ;; In case next buffer is not the one holding todos-current-todos-file.
   (todos-show))
 
-(defun todos-edit-item-header (&optional what)
-  "Edit date/time header of at least one item.
-
-Interactively, ask whether to edit year, month and day or day of
-the week, as well as time.  If there are marked items, apply the
-changes to all of these; otherwise, edit just the item at point.  
-
-Non-interactively, argument WHAT specifies whether to set the
-date from the Calendar or to today, or whether to edit only the
-date or day, or only the time."
-  (interactive)
+(defun todos-edit-item-header-1 (what &optional inc)
+  "Underlying function to edit items' date/time headers.
+
+The argument WHAT (passed by invoking commands) specifies what
+part of the header to edit; possible values are these symbols:
+`date', to edit the year, month, and day of the date string;
+`time', to edit just the time string; `calendar', to select the
+date from the Calendar; `today', to set the date to today's date;
+`dayname', to set the date string to the name of a day or to
+change the day name; and `year', `month' or `day', to edit only
+these respective parts of the date string (`day' is the number of
+the given day of the month, and `month' is either the name of the
+given month or its number, depending on the value of
+`calendar-date-display-form').
+
+The optional argument INC is a positive or negative integer
+\(passed by invoking commands as a numerical prefix argument)
+that in conjunction with the WHAT values `year', `month' or
+`day', increments or decrements the specified date string
+component by the specified number of suitable units, i.e., years,
+months, or days, with automatic adjustment of the other date
+string components as necessary.
+
+If there are marked items, apply the same edit to all of these;
+otherwise, edit just the item at point."
   (let* ((cat (todos-current-category))
          (marked (assoc cat todos-categories-with-marks))
-         (first t)                      ; Match only first of marked items.
+         (first t)
          (todos-date-from-calendar t)
-         ndate ntime nheader)
+         (buffer-read-only nil)
+         ndate ntime year monthname month day
+         dayname)       ; Needed by calendar-date-display-form.
     (save-excursion
       (or (and marked (goto-char (point-min))) (todos-item-start))
-      (catch 'stop
+      (catch 'end
         (while (not (eobp))
           (and marked
                (while (not (todos-marked-item-p))
                  (todos-forward-item)
-                 (and (eobp) (throw 'stop nil))))
+                 (and (eobp) (throw 'end nil))))
           (re-search-forward (concat todos-date-string-start "\\(?1:"
                                      todos-date-pattern
-                                     "\\)\\(?2: " diary-time-regexp "\\)?")
+                                     "\\)\\(?2: " diary-time-regexp "\\)?"
+                                     (regexp-quote todos-nondiary-end) "?")
                              (line-end-position) t)
           (let* ((odate (match-string-no-properties 1))
                  (otime (match-string-no-properties 2))
-                 (buffer-read-only))
-            (cond ((eq what 'today)
-                   (progn
-                     (setq ndate (calendar-date-string
-                                  (calendar-current-date) t t))
-                     (replace-match ndate nil nil nil 1)))
-                  ((eq what 'calendar)
-                   (setq ndate (save-match-data (todos-set-date-from-calendar)))
-                   (replace-match ndate nil nil nil 1))
-                  (t
-                   (unless (eq what 'timeonly)
-                     (when first
-                       (setq ndate (if (save-match-data
-                                         (string-match "[0-9]+" odate))
-                                       (if (y-or-n-p "Change date? ")
-                                           (todos-read-date)
-                                         (todos-read-dayname))
-                                     (if (y-or-n-p "Change day? ")
-                                         (todos-read-dayname)
-                                       (todos-read-date)))))
-                     (replace-match ndate nil nil nil 1))
-                   (unless (eq what 'dateonly)
-                     (when first
-                       (setq ntime (save-match-data (todos-read-time)))
-                       (when (< 0 (length ntime))
-                         (setq ntime (concat " " ntime))))
-                     (if otime
-                         (replace-match ntime nil nil nil 2)
-                       (goto-char (match-end 1))
-                       (insert ntime)))))
+                 (omonthname (match-string-no-properties 6))
+                 (omonth (match-string-no-properties 7))
+                 (oday (match-string-no-properties 8))
+                 (oyear (match-string-no-properties 9))
+                 (tmn-array todos-month-name-array)
+                 (mlist (append tmn-array nil))
+                 (tma-array todos-month-abbrev-array)
+                 (mablist (append tma-array nil))
+                 (yy (and oyear (unless (string= oyear "*")
+                                  (string-to-number oyear))))
+                 (mm (or (and omonth (unless (string= omonth "*")
+                                       (string-to-number omonth)))
+                         (1+ (- (length mlist)
+                                (length (or (member omonthname mlist)
+                                            (member omonthname mablist)))))))
+                 (dd (and oday (unless (string= oday "*")
+                                 (string-to-number oday)))))
+            ;; If there are marked items, use only the first to set
+            ;; header changes, and apply these to all marked items.
+            (when first
+              (cond
+               ((eq what 'date)
+                (setq ndate (todos-read-date)))
+               ((eq what 'calendar)
+                (setq ndate (save-match-data (todos-set-date-from-calendar))))
+               ((eq what 'today)
+                (setq ndate (calendar-date-string (calendar-current-date) t t)))
+               ((eq what 'dayname)
+                (setq ndate (todos-read-dayname)))
+               ((eq what 'time)
+                (setq ntime (save-match-data (todos-read-time)))
+                (when (> (length ntime) 0)
+                  (setq ntime (concat " " ntime))))
+               ;; When date string consists only of a day name,
+               ;; passing other date components is a NOP.
+               ((and (memq what '(year month day))
+                     (not (or oyear omonth oday))))
+               ((eq what 'year)
+                (setq day oday
+                      monthname omonthname
+                      month omonth
+                      year (cond ((not current-prefix-arg)
+                                  (todos-read-date 'year))
+                                 ((string= oyear "*")
+                                  (error "Cannot increment *"))
+                                 (t     ; FIXME: handle negative years
+                                  (number-to-string (+ yy inc))))))
+               ((eq what 'month)
+                (setf day oday
+                      year oyear
+                      (if (memq 'month calendar-date-display-form)
+                          month
+                        monthname)
+                      (cond ((not current-prefix-arg)
+                             (todos-read-date 'month))
+                            ((or (string= omonth "*") (= mm 13))
+                             (error "Cannot increment *"))
+                            (t
+                             (let ((mminc (+ mm inc))) 
+                               ;; Increment or decrement month by INC
+                               ;; modulo 12.
+                               (setq mm (% mminc 12))
+                               ;; If result is 0, make month December.
+                               (setq mm (if (= mm 0) 12 (abs mm)))
+                               ;; Adjust year if necessary.
+                               (setq year (or (and (cond ((> mminc 12)
+                                                          (+ yy (/ mminc 12)))
+                                                         ((< mminc 1)
+                                                          (- yy (/ mminc 12) 1))
+                                                         (t yy))
+                                                   (number-to-string yy))
+                                              oyear)))
+                             ;; Return the changed numerical month as
+                             ;; a string or the corresponding month name.
+                             (if omonth
+                                 (number-to-string mm)
+                               (aref tma-array (1- mm))))))
+                (let ((yy (string-to-number year)) ; 0 if year is "*".
+                      ;; When mm is 13 (corresponding to "*" as value
+                      ;; of month), this raises an args-out-of-range
+                      ;; error in calendar-last-day-of-month, so use 1
+                      ;; (corresponding to January) to get 31 days.
+                      (mm (if (= mm 13) 1 mm)))
+                  (if (> (string-to-number day)
+                         (calendar-last-day-of-month mm yy))
+                      (error "%s %s does not have %s days"
+                             (aref tmn-array (1- mm))
+                             (if (= mm 2) yy "") day))))
+               ((eq what 'day)
+                (setq year oyear
+                      month omonth
+                      monthname omonthname
+                      day (cond
+                           ((not current-prefix-arg)
+                            (todos-read-date 'day mm oyear))
+                           ((string= oday "*")
+                            (error "Cannot increment *"))
+                           ((or (string= omonth "*") (string= omonthname "*"))
+                            (setq dd (+ dd inc))
+                            (if (> dd 31)
+                                (error "A month cannot have more than 31 days")
+                              (number-to-string dd)))
+                           ;; Increment or decrement day by INC,
+                           ;; adjusting month and year if necessary
+                           ;; (if year is "*" assume current year to
+                           ;; calculate adjustment).
+                           (t
+                            (let* ((yy (or yy (calendar-extract-year
+                                               (calendar-current-date))))
+                                   (date (calendar-gregorian-from-absolute
+                                          (+ (calendar-absolute-from-gregorian
+                                              (list mm dd yy)) inc)))
+                                   (adjmm (nth 0 date)))
+                              ;; Set year and month(name) to adjusted values.
+                              (unless (string= year "*")
+                                (setq year (number-to-string (nth 2 date))))
+                              (if month
+                                  (setq month (number-to-string adjmm))
+                                (setq monthname (aref tma-array (1- adjmm))))
+                              ;; Return changed numerical day as a string.
+                              (number-to-string (nth 1 date)))))))))
+            ;; If new year, month or day date string components were
+            ;; calculated, rebuild the whole date string from them.
+            (when (memq what '(year month day))
+              (if (or oyear omonth omonthname oday)
+                  (setq ndate (mapconcat 'eval calendar-date-display-form ""))
+                (message "Cannot edit date component of empty date string")))
+            (when ndate (replace-match ndate nil nil nil 1))
+            ;; Add new time string to the header, if it was supplied.
+            (when ntime
+              (if otime
+                  (replace-match ntime nil nil nil 2)
+                (goto-char (match-end 1))
+                (insert ntime)))
             (setq todos-date-from-calendar nil)
             (setq first nil))
+          ;; Apply the changes to the first marked item header to the
+          ;; remaining marked items.  If there are no marked items,
+          ;; we're finished.
           (if marked
               (todos-forward-item)
             (goto-char (point-max))))))))
 
-(defun todos-edit-item-date ()
-  "Prompt for and apply changes to current item's date."
+(defun todos-edit-item-header ()
+  "Interactively edit at least the date of item's date/time header.
+If user option `todos-always-add-time-string' is non-nil, also
+edit item's time string."
+  (interactive)
+  (todos-edit-item-header-1 'date)
+  (when todos-always-add-time-string
+    (todos-edit-item-time)))
+
+(defun todos-edit-item-time ()
+  "Interactively edit the time string of item's date/time header."
   (interactive)
-  (todos-edit-item-header 'dateonly))
+  (todos-edit-item-header-1 'time))
 
 (defun todos-edit-item-date-from-calendar ()
-  "Prompt for changes to current item's date and apply from Calendar."
+  "Interactively edit item's date using the Calendar."
   (interactive)
-  (todos-edit-item-header 'calendar))
+  (todos-edit-item-header-1 'calendar))
 
-(defun todos-edit-item-date-is-today ()
-  "Set item date to today's date."
+(defun todos-edit-item-date-to-today ()
+  "Set item's date to today's date."
   (interactive)
-  (todos-edit-item-header 'today))
- 
-(defun todos-edit-item-time ()
-  "Prompt For and apply changes to current item's time."
+  (todos-edit-item-header-1 'today))
+
+(defun todos-edit-item-date-day-name ()
+  "Replace item's date with the name of a day of the week."
   (interactive)
-  (todos-edit-item-header 'timeonly))
+  (todos-edit-item-header-1 'dayname))
+
+(defun todos-edit-item-date-year (&optional inc)
+  "Interactively edit the year of item's date string.
+With prefix argument INC a positive or negative integer,
+increment or decrement the year by INC."
+  (interactive "p")
+  (todos-edit-item-header-1 'year inc))
+
+(defun todos-edit-item-date-month (&optional inc)
+  "Interactively edit the month of item's date string.
+With prefix argument INC a positive or negative integer,
+increment or decrement the month by INC."
+  (interactive "p")
+  (todos-edit-item-header-1 'month inc))
+
+(defun todos-edit-item-date-day (&optional inc)
+  "Interactively edit the day of the month of item's date string.
+With prefix argument INC a positive or negative integer,
+increment or decrement the day by INC."
+  (interactive "p")
+  (todos-edit-item-header-1 'day inc))
 
 (defun todos-edit-item-diary-inclusion ()
   "Change diary status of one or more todo items in this category.